The invention relates to a vehicle seat belt system comprising a reversible belt tensioner adapted to apply a belt tightening force on one or more predetermined levels to a belt strap of a seat belt.
Reversible tensioning of the belt strap is not only used to largely eliminate the belt slack prior to an accident and to prevent the vehicle occupant as far as possible from being displaced forward, but can also fulfill a comfort function and impart more safety to the vehicle occupant by more tense contact of the belt strap in particular driving situations.
The belt tensioners used for this purpose can achieve comparatively smooth and almost unnoticed contact of the belt strap to the body by appropriate control, wherein the belt tightening force can be continuously increased and reduced. Such control is especially interesting during cornering where a comfortable tensioning of the belt fixes the driver in a better way in his seat upon occurrence of transverse accelerations and accordingly conveys improved lateral support.